1. Technical Field
The inventive arrangements relate generally to video systems and more particularly to video systems that record or play back digitally encoded video sequences.
2. Description of Related Art
Digital televisions (DTV) and high-definition televisions (HDTV) are gaining popularity in today's consumer electronics marketplace. Many purchasers of these types of televisions also buy digital video recorders or players, such as a digital video disc (DVD) recorder or player, for purposes of viewing previously recorded programs or recording their favorite programs. Notably, the combination of a DTV (or an HDTV) and a digital video recorder or player can be an integral part of a home theater entertainment system.
A digital video recorder or player typically contains an MPEG decoder to decode the digitally encoded multimedia data that is stored on the discs that the recorder or player plays. If the digital video recorder or player is connected to a conventional (non-DTV or non-HDTV) television, the digitally encoded signal will be decoded by the digital video recorder's or player's MPEG decoder before being displayed on the conventional television. Significantly, however, many DTV's contain their own MPEG decoders, as the MPEG decoder in the majority of digital video recorders or players cannot handle the decoding of video signals for such televisions. As such, if a digital video recorder or player is connected to a DTV, the video signal read from the disc is remotely decoded by the DTV's decoder. This configuration can be referred to as a remote decoder arrangement.
There is, however, an important disadvantage to decoding digitally encoded signals with a remote DTV decoder. Namely, it is very difficult to perform trick modes in this type of arrangement. For example, oftentimes, a trick mode involves repeating a number of pictures in a video signal. As the bandwidth between the digital recorder and the DTV is limited, repeating pictures in the signal being fed to the DTV may cause the signal to exceed the maximum bit rate limit of the transmission channel. The problem is even more acute if the pictures are intra (I) pictures or predictive (P) pictures, as these pictures are generally encoded with more bits than the average picture.
Moreover, certain trick mode commands, such as a freeze or pause command, or a frame or field advance or slide show, can be problematic. Generally, a freeze command involves stopping and starting on a picture that may not necessarily be a precisely selected picture by the user. For example a product designer may elect to freeze only on a reference picture. A frame advance command is more precise in that every frame is frozen for a user selected time period. A varied form of frame advance known as a slide show is also precise in that every frame is frozen for a predetermined period. Each frame is displayed for a long, but known period of time. The slide show may also be thought of as a very slow forward trick mode. These trick modes may require the ability to freeze on each frame (or field) for an unlimited duration or for a duration not easily supported with MPEG techniques. The problem occurs, when an advance or slide show trick mode is initiated, there is no way to determine exactly how long the trick mode will remain in effect. Consequently, it is impossible to calculate how many times a particular picture will be displayed during this type of trick mode. This uncertainty can interfere with the display order of the pictures being transferred to the decoder in the DTV, as the DTV decoder is not under the control of the digital video recorder and has no way of knowing that a freeze, advance or slide show trick mode has been initiated. Moreover, even when the duration of such trick modes is predetermined, a trick mode utilizing a repeating B-frame can still cause errors relating to picture sequencing by the decoder. Thus, a need exists for a method and system for overcoming the limitations described above without increasing system costs or complexity.